全文获取类型
收费全文 | 3164篇 |
免费 | 178篇 |
国内免费 | 23篇 |
专业分类
耳鼻咽喉 | 29篇 |
儿科学 | 166篇 |
妇产科学 | 31篇 |
基础医学 | 366篇 |
口腔科学 | 24篇 |
临床医学 | 276篇 |
内科学 | 901篇 |
皮肤病学 | 47篇 |
神经病学 | 230篇 |
特种医学 | 164篇 |
外国民族医学 | 2篇 |
外科学 | 444篇 |
综合类 | 25篇 |
预防医学 | 131篇 |
眼科学 | 200篇 |
药学 | 183篇 |
1篇 | |
中国医学 | 1篇 |
肿瘤学 | 144篇 |
出版年
2022年 | 22篇 |
2021年 | 46篇 |
2020年 | 25篇 |
2019年 | 48篇 |
2018年 | 73篇 |
2017年 | 40篇 |
2016年 | 36篇 |
2015年 | 35篇 |
2014年 | 62篇 |
2013年 | 108篇 |
2012年 | 117篇 |
2011年 | 129篇 |
2010年 | 101篇 |
2009年 | 95篇 |
2008年 | 122篇 |
2007年 | 178篇 |
2006年 | 166篇 |
2005年 | 150篇 |
2004年 | 117篇 |
2003年 | 105篇 |
2002年 | 125篇 |
2001年 | 101篇 |
2000年 | 118篇 |
1999年 | 97篇 |
1998年 | 67篇 |
1997年 | 62篇 |
1996年 | 61篇 |
1995年 | 34篇 |
1994年 | 43篇 |
1993年 | 31篇 |
1992年 | 68篇 |
1991年 | 51篇 |
1990年 | 62篇 |
1989年 | 77篇 |
1988年 | 49篇 |
1987年 | 58篇 |
1986年 | 54篇 |
1985年 | 40篇 |
1984年 | 40篇 |
1983年 | 36篇 |
1982年 | 19篇 |
1981年 | 21篇 |
1979年 | 19篇 |
1975年 | 21篇 |
1974年 | 21篇 |
1970年 | 21篇 |
1969年 | 17篇 |
1967年 | 16篇 |
1966年 | 18篇 |
1965年 | 21篇 |
排序方式: 共有3365条查询结果,搜索用时 15 毫秒
71.
72.
73.
74.
Yuli R Tak Rinka MP Van Zundert Rowella CWM Kuijpers Boukje S Van Vlokhoven Hettie FW Rensink Rutger CME Engels 《BMC public health》2012,12(1):21
Background
The incidence of depressive symptoms increases during adolescence, from 10.0% to 24.5% at age 11 to 15, respectively. Experiencing elevated levels of depressive symptoms increases the risk of a depressive disorder in adulthood. A universal school-based depression prevention program Op Volle Kracht (OVK) was developed, based on the Penn Resiliency Program, aimed at preventing the increase of depressive symptoms during adolescence and enhancing positive development. In this study the effectiveness of OVK will be tested and possible mediators of program effects will be focus of study as well. 相似文献75.
76.
77.
The tetrapeptide Acetyl-N-Ser-Asp-Lys-Pro (AcSDKP, Seraspenide; Ipsen- Biotech, Paris, France), an inhibitor of murine spleen colony-forming units reduces the number and the percentage in DNA synthesis of progenitors from human unfractionated bone marrow. To determine whether AcSDKP may directly affect the growth potential of purified progenitors even at the most primitive level, CD34+HLA-DRhigh and CD34++HLA-DRlow cells were highly purified by cell sorting. Then, CD34+ subsets were stimulated in liquid culture with combinations of growth factors (GFs) and AcSDKP was added for 20 hours or 6 days and cells plated in methylcellulose. After a 20-hour incubation, we show that AcSDKP (at 10(-10) mol/L) significantly inhibits the colony formation of both CD34+ subsets. Moreover, when added daily for 6 days, AcSDKP: (1) reduces the proliferation of both CD34+ cell fractions stimulated by 3 or 7 GFs, and (2) decreases the number of progenitors generated from the CD34+HLA-DRhigh and CD34++HLA-DRlow cell fractions. Furthermore, we show for the first time, using both high proliferative potential cell and long-term culture initiating cell assays, that AcSDKP inhibits the most primitive cells contained in the CD34++HLA-DRlow subpopulation. Finally, by using limiting dilution assays we demonstrated that AcSDKP acts directly at a single cell level and that its inhibitory effect is reversible and dose dependent. 相似文献
78.
Initiation of the extrinsic pathway of coagulation by human and rabbit alveolar macrophages: a kinetic study 总被引:3,自引:0,他引:3
We examined assembly and expression of the factor X activating complex on human and rabbit alveolar macrophages. Kinetic parameters of the factor X activating reaction were determined by functional titrations of factors VII and X with macrophage tissue factor (TF) added. We found rapid activation of factor X to Xa on alveolar macrophage surfaces. Detection of rapid factor Xa formation on macrophages required addition of exogenous factors VII and X. At plasma concentrations of the purified factors, factor Xa was formed on freshly isolated macrophages at approximately 5.4 pmol/min/10(6) cells. After macrophage maturation in culture for 20 hours with LPS (endotoxin) added, the factor X activation rate was increased two- to sixfold. The km' (apparent km) of TF-factor VII enzymatic complexes assembled on alveolar macrophages for factor X were (258 +/- 55 and 475 +/- 264 nmol/L for human and rabbit cells, respectively). The km' did not change during macrophage maturation in culture, but V'max (apparent Vmax) was consistently increased. The K1/2 of human factor VII (concentrations giving half maximal rates of factor X activation) for the interaction with human and rabbit alveolar macrophage TF were 0.191 +/- 0.096 and 1.7 +/- 0.7 etamol/L, respectively. The K1/2 were not significantly changed after maturation, whereas rates of Xa formation at saturation with factor VII were increased. The fast rates of factor X activation observed at physiologic concentrations of plasma-derived factors VII and X indicate that TF on alveolar macrophages is likely to provide sites for binding of factor VII and activation of factor X in vivo during clotting reactions associated with alveolar edema and inflammation. 相似文献
79.
This work attempted to study the segmental wall motion on left ventriculograms, in terms of segmental shortening, velocity of segmental shortening, and temporal sequences of various events in systole as well as in diastole. The ability of such a method to characterize patterns of normal regional wall motion and to detect mild abnormalities such as isolated asynchronisms, was tested on two groups of patients. Group I included 25 patients presenting evidence of a normal left ventricle (LV) after left heart catheterization. Group II consisted of 21 patients suffering from an isolated pure idiopathic mitral valve prolapse (MVP), with no mitral insufficiency and with an unaffected global LV function. In all patients left ventriculography was filmed in the right anterior oblique view at a rate of 50 frames/s. For each patient a cycle was chosen, distant from any premature beat, with acceptably contrasted outlines, and a quantitative frame by frame study of the motion of 10 segments was performed using a semiautomated method derived from the Stanford method. In the control group (Group I), analysis of the segmental motion by means of this method demonstrates a mild nonuniformity of the normal wall motion. This is principally marked by a stronger and faster contraction in anterolateral segments (segments 7, 8, 9) and by a shorter duration of the contraction in this region. In contrast the MVP group (Group II), exhibited a frank asynergy of the anterolateral region occurring from end systole to early diastole.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
80.
Factors affecting the transduction of pluripotent hematopoietic stem cells: long-term expression of a human adenosine deaminase gene in mice 总被引:5,自引:0,他引:5
An amphotropic retroviral vector, LgAL(delta Mo + PyF101) containing a human adenosine deaminase (ADA) cDNA was used to optimize procedures for the lasting genetic modification of the hematopoietic system of mice. The highest number of retrovirally infected cells in the hematopoietic tissues of long-term reconstituted mice was observed after transplantation of bone marrow (BM) cells that had been cocultured in the presence of both interleukin-1 alpha (IL-1 alpha) and IL-3. A significantly lower number was detected when IL-1 alpha was omitted from such cocultures. The yield of cells that generate spleen colony-forming cells (CFU-S) in the BM of lethally irradiated recipients (MRA-CFU-S) significantly improved on inclusion of the adherent cell fraction of cocultures in the transplant. Retroviral integration patterns in MRA-CFU-S-derived spleen colonies showed that an MRA-CFU-S can produce many CFU-S during BM regeneration. Expression of hADA was detected in the circulating white blood cells of long-term reconstituted animals, demonstrating that the LgAL(delta Mo + PyF101) vector is capable of directing the sustained expression of hADA, and in approximately 35% of the transduced MRA-CFU-S-derived spleen colonies. These results should facilitate the development of gene therapy protocols for the treatment of severe combined immunodeficiency caused by a lack of functional ADA. 相似文献